The present disclosure relates to a coordinate measuring machine, and more particularly to a portable articulated arm coordinate measuring machine having a connector on a probe end of the coordinate measuring machine that allows accessory devices which use structured light for non-contact three dimensional measurement to be removably connected to the coordinate measuring machine.
Portable articulated arm coordinate measuring machines (AACMMs) have found widespread use in the manufacturing or production of parts where there is a need to rapidly and accurately verify the dimensions of the part during various stages of the manufacturing or production (e.g., machining) of the part. Portable AACMMs represent a vast improvement over known stationary or fixed, cost-intensive and relatively difficult to use measurement installations, particularly in the amount of time it takes to perform dimensional measurements of relatively complex parts. Typically, a user of a portable AACMM simply guides a probe along the surface of the part or object to be measured. The measurement data are then recorded and provided to the user. In some cases, the data are provided to the user in visual form, for example, three-dimensional (3-D) form on a computer screen. In other cases, the data are provided to the user in numeric form, for example when measuring the diameter of a hole, the text “Diameter=1.0034” is displayed on a computer screen.
An example of a prior art portable articulated arm CMM is disclosed in commonly assigned U.S. Pat. No. 5,402,582 ('582), which is incorporated herein by reference in its entirety. The '582 patent discloses a 3-D measuring system comprised of a manually-operated articulated arm CMM having a support base on one end and a measurement probe at the other end. Commonly assigned U.S. Pat. No. 5,611,147 (147), which is incorporated herein by reference in its entirety, discloses a similar articulated arm CMM. In the '147 patent, the articulated arm CMM includes a number of features including an additional rotational axis at the probe end, thereby providing for an arm with either a two-two-two or a two-two-three axis configuration (the latter case being a seven axis arm).
Three-dimensional surfaces may be measured using non-contact techniques as well. One type of non-contact device, sometimes referred to as a laser line probe (LLP) or laser line scanner, emits a laser light either on a spot, or along a line. An imaging device, such as a charge-coupled device (CCD) for example, is positioned adjacent the laser. The laser is arranged to emit a line of light which is reflected off of the surface. The surface of the object being measured causes a diffuse reflection which is captured by the imaging device. The image of the reflected line on the sensor will change as the distance between the sensor and the surface changes. By knowing the relationship between the imaging sensor and the laser and the position of the laser image on the sensor, triangulation methods may be used to measure three-dimensional coordinates of points on the surface.
It is sometimes desirable to measure 3D coordinates of smoothly continuous edge points using one or more cameras integrated into an AACMM without using additional probes. There is a need to obtain such 3D coordinates with relatively high accuracy and high density and without errors that may be introduced by 3D noncontact measuring devices such as an LLP or structured light scanner.
While existing CMM's are suitable for their intended purposes, what is needed is a portable AACMM that has certain features of embodiments of the present invention.